Following the emergence of retail parks in the late 1970s in Britain, they have grown in number, scale and degree of retail specialisation. Some continue to form concentrations offering primarily ‘bulky goods' shopping, while others have diversified to offer traditional ‘high street' functions from stores indistinguishable from their town and city centre equivalents. Consequently, in some cases the emergence of new ‘high streets' in the suburbs can be posited. In view of the potential impact such developments might have on traditional shopping centres, this study reviews the development of retail parks in Britain in recent years, and examines the commercial impact of a retail park in the process of transition towards a suburban ‘high street'. Evidence from surveys in 2003 and 2004 of the Fforestfach Retail Park in the greater Swansea area indicates that the transition towards a suburban ‘high street' is beginning to impact significantly on traditional shopping centres of all types. It was evident that even small additions of ‘high street' functions between the two recent survey dates elicited a statistically significant strengthening of their trading impact. Consequently, it is suggested that upgraded retail parks are likely to become stronger competitive threats to the full range of district, town and city centres if ‘high street' functions continue to be added to retail parks.